The present invention relates to a method of removing arsenic, particularly arsines, in hydrocarbons particularly gaseous hydrocarbons such as LPG.
Recently, accompanying the effective utilization and quality improvement of heavy fractions of crude oil, reforming conversion of the heavy fractions to gasoline by means of fluidized bed catalytic cracking apparatus has been put into practice. C.sub.3 and C.sub.4 LPG fractions, particularly C.sub.3 LPG fraction, produced as by products; of the conversion process, sometimes contain hydrogen arsenide; depending on the kind of crude oil.
When using C.sub.3 LPG fraction in industrial uses, it is usually separated into a propylene fraction and a propane fraction by a distillation process, whereby the hydrogen arsenide is distributed in the propylene fraction. The hydrogen arsenide in the propylene fraction functions as a catalyst poison in a later reaction process, so that removal thereof is a pressing problem.
Heretofore, there have been proposed many methods of removing arsenic contained in petroleum fractions. Typical examples thereof are: U.S. Pat. No. 3,093,574 wherein liquid naphtha containing arsenic is treated by silica gel impregnated with sulfuric acid; U.S. Pat. No. 2,779,715 wherein arsenic in a petroleum fraction is treated by an alkaline metal or alkaline earth metal salt in the presence of a catalyst consisting of noble metal and alumina; U.S. Pat. No. 2,781,297 wherein arsenic in a petroleum fraction is treated by a salt of copper or a metal which has a smaller electromotive force than copper; and Japanese patent application No. 55/55,511/77 (laid-open No. 143,607/78) wherein arsenic in a petroleum fraction is subjected to oxidization treatment by means of an organic oxidizing material or oxygen-containing gas and the resultant oxidized arsenic is separated and removed by distillation. However, these methods have various drawbacks in that a minor content of arsenic is difficult to remove, investment cost accompanying pre-treatment and post-treatment is considerable, and production preparation costs of arsenic-removing agent are rather expensive, and a polymer is liable to be produced because of polymerization when treating a petroleum fraction containing highly reactive olefin and diolefin.